Simple Machines: Force, Work and Distance

• A simple machine reduces effort needed for work by changing force's direction or amount.
• These machines often have few or no moving parts, simplifying work.
• Simple machines can multiply force, but at the cost of distance.
• They can also multiply distance by applying more force.
• Simple machines can be used to change the direction of force applied.

Simple Machines Variables

• Work (W) is measured in Joules (J).
• Force (F) is measured in Newtons (N).
• Distance (d) is measured in Meters (m).
• Ideal Mechanical Advantage (IMA) is a ratio without units.
• Actual Mechanical Advantage (AMA) is a ratio without units.
• A simple machine makes work easier by:
  • Multiplying the force applied to an object using tools like hammers, hydraulic lifts, pliers, and crowbars.
  • Transforming energy using engines, transformers, and other appliances.
  • Multiplying speed or distance using tools like baseball bats, brooms, and rollers.
  • Changing the direction of force.

Classification of Simple Machines

• Inclined Plane
• Lever
• Screw
• Wedge
• Pulley
• Wheel and Axle

Mechanical Advantage

• Mechanical Advantage (MA) is the number of times a machine increases an input force.
• The theoretical advantage can be computed by dividing the distance of the effort to the load.
• The number of times the machine actually helped in doing work is the AMA.

AMA

• AMA is determined by measuring actual forces or the ratio of output force to input force.
• Necessary to know the force applied (effort) and the force produced (load) to understand AMA.
• AMA is calculated as Load (resistance) / Effort (input force).
• IMA assumes 100% efficiency, based on measurement distances such as how far you push divided by how far the object moves.
• AMA considers the inefficiency of the machine and calculates energy lost as heat

Efficiency of Machines

• 100% efficiency can never be achieved due to friction, which converts input work into useless heat.

Levers

• Levers are used to lift heavy loads.
• They have three parts: Fulcrum, effort, and load
• A lever is a rigid bar that rotates on a fixed point called the fulcrum.
• It lifts a load or resistance by applying effort.
• Greater distance from effort to fulcrum relative to the load provides a mechanical advantage.

Lever Descriptors

• Fulcrum/pivot holds lever in place.
• Effort/applied force is where you apply the force.
• Load/resistance is the force the lever acts against.

Lever Classification

• First Class: Fulcrum between load and effort; MA can be <1, =1, or >1.
• Second Class: Load between fulcrum and effort; MA is always >1.
• Third Class: Effort between fulcrum and load; MA is always <1.
• In a first class lever, the fulcrum is between the load and the effort.
• When the fulcrum is closer to the load, less effort is needed to move it.
• First class levers facilitate lifting large loads with minimal effort.
• A teeter-totter, car jack, and crowbar are first class levers.
• If the load is closer to the fulcrum than the effort in a second class lever, then less effort is required to move the load.
• A wheelbarrow, bottle opener, and oars are second class levers.
• In a third class lever, the effort is between the load and fulcrum.
• Third class levers cannot give MA, regardless of where you applied force.